1. Field of the Invention
The present invention relates to an apparatus and a method for Automatic Repeat reQuest (ARQ) in a wireless communication system. More particularly, the present invention relates to an apparatus and a method for performing effective ARQ feedback in the wireless communication system.
2. Description of the Related Art
A wireless communication system can encounter data error according to the channel condition of the radio resource. In this regard, the wireless communication system controls and recovers the data error using an Automatic Repeat reQuest (ARQ) scheme to increase the transmission reliability.
Using the ARQ scheme, a receiving end informs a transmitting end of success or failure of the packet reception from the transmitting end. For example, when the packets received from the transmitting end have no error, the receiving end may send ACKnowledgement (ACK) information to the transmitting end. In contrast, when the packets received from the transmitting end have error, the receiving end sends Non-ACKnowledgement (NACK) information to the transmitting end. Herein, a series of the operations for the receiving end to transmit the success or the failure of the packet reception to the transmitting end is referred to as an ARQ feedback.
Based on the ARQ feedback, the transmitting end can determine whether the packets transmitted to the receiving end are successfully received. When determining that there has been successful packet reception at the receiving end based on the ARQ feedback, the transmitting end deletes the packets successfully received at the receiving end from its transmission buffer. When determining that there has been packet reception failure at the receiving end through the ARQ feedback, the transmitting end retransmits the original packets of the reception failure of the receiving end to the receiving end for the data error recovery at the receiving end.
The receiving end performs the ARQ feedback in various manners according to a communication standard. For example, the receiving end may perform the ARQ feedback only when the received packets are corrupted. Alternatively, the receiving end can perform the ARQ feedback according to ARQ feedback indication information in data received from the transmitting end. Alternatively, without determining whether to perform the ARQ feedback or defining the ARQ feedback time, the receiving end itself may determine and carry out the ARQ feedback.
When the receiving end performs the ARQ feedback according to the ARQ feedback indication information provided from the transmitting end, the transmitting end, which has to include an ARQ feedback request indicator into every ARQ block, is subject to regular overhead. In addition, since the receiving end cannot perform the ARQ feedback without the ARQ feedback indication of the transmitting end, the degree of freedom in the ARQ feedback operation of the receiving end deteriorates.
When the receiving end itself determines and performs the ARQ feedback, the transmitting end cannot know the ARQ feedback time of the receiving end. As a result, the transmitting end cannot smoothly allocate the resource for the ARQ feedback of the receiving end. In addition, since the transmitting end performs the ARQ depending on the ARQ feedback of the receiving end, the ARQ performance disadvantageously degrades.